Durex recently asked its Facebook followers to pick which city they thought should get Durex SOS Condoms, which, according to the company’s website, are provided on a rush basis to customers via a smartphone app.

According to Durex’s website, London (with 594 votes) did not win. Nor did Paris (688), New York (363), or Kuala Lumpur (1,420). Tuscaloosa wasn’t even in the running. Pranksters, according to Bloomberg, swung the vote to Batman (1,731), capital city of a conservative Muslim province in Turkey, where condoms are unwelcome.

These days, say experts, any brand that wants to remain engaged with its audience has to have a social media marketing campaign. But such campaigns, they say, are opportunities for abuse.

McDonald’s in 2012, according to Bloomberg, sponsored a Twitter campaign that invited patrons to post stories of their favorite McDonald’s experiences. Instead of a torrent of warm, feel-good recollections, McDonald’s got snarky Tweets that included the following:

“My memories of walking into a McDonald’s: The sensory experience of inhaling deeply from a freshly-opened can of dog food.”

And this one: “McDonald’s customers don’t want to tell #McDStories. They just want their fries, mechanically separated chicken parts and wallow in shame.”

McDonald’s, says Bloomberg, ended the promotion less than two hours after its debut.

The problem in these two cases—and in many others—say experts, is that the campaigns gave respondents too much leeway.

Ben Foster, senior vice present of digital media for Ketchum public relations, says companies make a mistake by not keeping close watch on what the public is saying.

Others err by thinking that monitoring software can take the place of human lookouts.

“People have taken a lot of shortcuts when it comes to listening,” Foster tells ABC News.

“A machine cannot do it. We advise clients: actually go in and see what people are saying.” Software, he says, can sometimes fail to detect an ominous comment because the sender has misspelled the “red flag” words or phrases the automatic filter was supposed to detect.

Make sure, he says, that the person tasked with monitoring takes the job seriously. “Don’t just look for the youngest person in the room to run it. Put an expert in charge.”

How quickly a company reacts when it detects the first sign of trouble can be critical, King says.

Nikon launched what seemed to be an innocuous enough Facebook campaign to promote its lenses and other photography equipment. It contained the statement, “A photographer is only as good as the equipment he uses, and a good lens is essential to taking good pictures!”

Nikon’s Facebook page, according to Tineka Smith of Computer Business Review, soon filled with complaints from photo buffs who took umbrage at the insinuation they were less important than the lens.

Nikon retreated, posting: “We know some of you took offense, and we apologize, as it was not our intent to insult any of our friends. A great picture is possible anytime and anywhere.”

King doesn’t recommend censoring customers’ comments, because to do so may “only feed the anger.” But companies need to monitor responses and respond quickly when they see trouble. Every situation is unique. “There’s no playbook,” he says. “You’ve got to watch the nuances, make those decision in real time: are people really upset? Is it really a protest? The quicker you react makes a difference.”

A company that recognizes and responds promptly to someone genuinely offended, says King, “can stop the viral juggernaut.”

Sometimes, he says, it takes only one spark to ignite a long-smoldering mass of customer resentment — ones of which the social marketers may not be aware. A company could get advance warning of such a danger if it linked its customer service department to its social media department. “But few do,” says King. Many social media disasters he calls “self-inflicted wounds.”